gallivm: Fix build with LLVM >= 3.6 r215967.

gallivm: Fix build with LLVM >= 3.6 r215967.

This LLVM 3.6 commit changed EngineBuilder constructor.

commit 3f4ed32b4398eaf4fe0080d8001ba01e6c2f43c8
Author: Rafael Espindola <rafael.espindola@gmail.com>
Date:   Tue Aug 19 04:04:25 2014 +0000

    Make it explicit that ExecutionEngine takes ownership of the modules.

    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215967 91177308-0d34-0410-b5e6-96231b3b80d8

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-and-Tested-by: Michel Dänzer <michel.daenzer@amd.com>